Implementing Responsive Landing Pages in Marketo require some HTML/CSS understanding. You can see some posts on how to achieve them from Edward Unthank @ Yesler - https://community.marketo.com/MarketoDiscussionDetail?id=90650000000PcgZAAS.
However, responsive emails are a breeze. To the specific comment on android phones - do note that the gmail app on android phones doesnt support media queries. http://stackoverflow.com/questions/13604300/responsive-emails-on-gmail-app-android.
All the email templates on the templates marketplace use the Ink framework http://zurb.com/ink/ - which uses media queries to determine device size - unfortunately some devices do not support the mediaquery call.
Campaign Monitor has an extensive list - http://www.campaignmonitor.com/guides/mobile/#mobile-support
Regards,
Alok